mm_broadband_modem_mbim: Add Support for get model name by AT in mbim.
Add support for getting model names via at in mbim. MM will use
the AT command to get the model name, if MM fails to get the model
name, MM will set vid:pid as the default model name.
Test on L860 Linux Device, use mmcli -L, it can show: "/org/free
desktop/ModemManager1/Modem/0 [Intel] L860-#16 (closed) LTE Module"
Edited by Sun XinZhao